Re: it isn't strange?!

*To*: mathgroup at smc.vnet.net*Subject*: [mg116126] Re: it isn't strange?!*From*: Derivator <derivatorb at gmail.com>*Date*: Thu, 3 Feb 2011 05:27:38 -0500 (EST)*References*: <iibds7$nnd$1@smc.vnet.net>

On 2 feb, 12:06, olfa <olfa.mra... at yahoo.fr> wrote: > Hi Mathematica community, > > here is my pb: > > input: > Reduce[Max[a, b] = Max[c, d], c, Reals] > output: > (d < Max[a, b] && c = Max[a, b]) || (d = Max[a, b] && c <= Max[a, > b]) > > when testing this output with 2 initialisations: > d = 2 a = 4 b = 3 c = 6 here d < Max[4, 3] but c is not equal to > Max[4, 3] > > d = 4 a = 4 b = 3 c = 6 here d = Max[4, 3] but c is not <= to > Max[4, 3] > > where is the pb?! Actually I cannot see any problem. In the examples you give the initial proposition Max[a, b] == Max[c, d] is false, and the equivalent proposition generated by Reduce is equally false. If you consider all possible situations you will find that Max[a, b] == Max[c, d] is indeed always equivalent to (d <= Max[a, b] && c == Max[a, b]) || (d == Max[a, b] && c <= Max[a,b]): both are simultaneously true of false. Note that you do not really use a and b separately, only the combination Max[a,b], so you need to consider only if (m == Max[c, d]) is equivalent to (d < m && c == m) || (d == m && c <= m). Good luck L.L.